The prevailing approach of total clearing to contain the spread of invasive plants (IP) in South Africa is generating enormouslignocellulosic wastes. This study examined the possibility of utilizing these wastes in the production of geopolymercomposites for use in outdoor environments. Untreated wood particles from Acacia mearnsii and A. longifolia, as well assugarcane bagasse residues, were incorporated into a geopolymer matrix developed from a binary precursor system of 75%fly ash and 25% metakaolin. The variables considered included precursor-activator ratio (PA), curing pattern (CP), lignocellulosicmaterial (LM), and alkali concentration (Mcon). The production process was established using a mixed factorialexperimental design. PA and CP were considered at 2 levels, while LM and MCon were considered at 3 levels. The densityof the boards exceeded 1 g cm−3 and are classified as high-density boards. The boards have comparable sorption propertiesto the cement-bonded particleboard according to the EN 632-2: 2007 standard. However, only A. longifolia boards producedwith 12 M NaOH and PA ratio of 2:1 met the mechanical strength requirements. Thermogravimetric analysis revealed thatthe boards are thermally stable. These results have shown that South African woody IPs are suitable for geopolymer woodcomposites, but there is still concern about their durability in the alkaline matrix. Scanning electron microscopy micrographsindicated mineralization of the particles and a partial degradation of hemicellulose was confirmed by Fourier transform infraredspectroscopy. Although the degraded components did not prevent geopolymer setting, there is need to further investigatethe extent and means of preventing degradation as this can derail the intended use of the product.